Method of inhibiting discoloration of color photographs



3,473,929 METHOD OF TNHIBITING DISCOLORATION OF COLOR PHOTOGRAPHS Roy A.lelfreys and Leslie A. Williams, Wealdstone, Harrow, England, assignorsto Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey NDrawing. Filed Sept. 9, 1965, Ser. No. 486,236 Int. Cl. G03c 7/30 US.Cl. 96--56 7 Claims ABSTRACT OF THE DISCLOSURE The discoloration ofcompletely processed color photographs caused by prolonged exposure tolight, elevated temperatures and elevated humidity is advantageouslyinhibited by imbibing in said photograph an aqueous solution of astabilizing compound having at least one tri- (hydroxymethyl)-methylgroup and then drying said photograph while it still contains asubstantial quantity of said stabilizing compound.

This invention relates to color photography and more particularly tomethods for preventing discoloration of photographic layers containingdye images.

The images of color photographs produced by many photographic processes,for example those processes involving the color development of imagewiseexposed photographic silver halide emulsion layers, comprise dyes whichare present in water permeable layers carried by a support such as paperor film base. These dyes are, in general, not highly stable, and socolor photographs tend to be discolored if exposed to bright light,particularly direct sunlight, or stored under adverse temperature andhumidity conditions for long periods. Discoloration can be due both todifferences between the fading rates of the dyes, usually cyan, magentaand yellow dyes, in the image, and to the formation of an overall stainfrom chemicals in the image-containing layers, or elsewhere. Such astain is sometimes termed print-out.

In photographic processes involving color development, the couplers maybe in the color developer solutions or may be incorporated in theemulsion layers. Examples of couplers which may be used in developersolutions are given in The Theory of the Photographic Process by C. E.K. Mees (revised edition, 1954) on pages 588589; examples of couplerswhich may be incorporated in emulsion layers are given on pages 598599.Dyes produced by color development are, in general, indoaniline,azomethine, indophenol and indamine dyes.

Materials for the production of color photographs by processes involvingcolor development are described on pages 305-307 of Principles of ColorPhotography, Evans, Hanson and Brewer (New York, 1953), and include thematerials well known under the registered trademarks Kodachrome,Kodacolor, Ektachrome and Ektacolor.

Many indophenol, indamine, indoaniline and azomethine dyes arerelatively unstable to light with the result that dye images in finishedcommercial color pictures have a tendency to fade, especially whensubjected to intense illumination for extended periods of time. This istrue whether the source of illumination is sunlight or tungsten orfluorescent lamps. The cyan dyes are generally relatively lesssusceptible to fading than the other dyes commonly used in colorphotography. In processes in which the couplers are incorporated in theemulsion layers or in plain gelatin layers in the film, furtherdifiiculty is caused by residual unused couplers which tends toprintnited States Patent 0 'ice out as a stain, usually a yellow stain,under the influence of light, especially in the highlight areas of thepicture. Magenta dye-forming couplers are generally more susceptible toprint-out than others.

One solution to the problem of fading of dye images and print-out ofresidual couplers in photographic layers would be to use only couplersand dyes which are inherently stable to light. This is seldom feasible,however, since the number of couplers and dyes suitable for use incommercial photographic color processes is somewhat limited and it isoften the case that the most suitable materials are not as stable asmight be desired. Therefore, the most satisfactory approach to thefading and print-out problem has been to choose couplers and dyessuitable for the particular photographic process and then attempt toprotect these compounds against the usually deleterious effects oflight.

In general, two methods have been suggested to prevent the discolorationof photographic layers. One of these comprises overcoating thephotographic layer to be protected with an ultraviolet light absorbingmaterial. Methods of this type are disclosed in Salminen et al., U.S.Patent 2,632,701 issued Mar. 24, 1953, and Edgerton et al., US. Patent2,747,996 issued May 29, 1956. The other method referred to comprisestreatment of photographic layers containing dye images with certainchemical compounds, particularly organic reducing agents orantioxidants, in order to stabilize the dye images and any residualcoupler in the photographic layers. Methods of this type are disclosedin Vittum, US. Patent 2,384,658 issued Sept. 11, 1955 and Mackey, US.Patent 2,579,435 issued Dec. 18, 1951. Methods of the latter type havebeen found to be entirely empirical. For example, although the reducingagents of the Vittum patent are useful, others of similar reducingproperties have no efiect on the stability of photographic dye images.Further, many reducing compounds which might suggest themselves asstabilizing agents not only have no stabilizing properties but actuallycause stain or destruction of dye images in photographic layers. It has,therefore, been difficult to find compounds having appreciable dyestabilizing or anti-print-out properties which are also free from otherundesirable characteristics. Therefore, although the above and othermethods have been suggested in the art for protecting coloredphotographic elements against discoloration due to fading or print-out,none has proven to be a complete solution to the problem and the searchfor new methods has continued.

It is an object of the present invention to provide a method forpreventing dye fading and print-out in processed color photographscomprising treating the said processed material with certain compoundscontaining at least one trimethylol methyl group. It is a further objectof the invention to provide color photographic materials includingfilms, transparencies and prints stabilized against discoloration underthe influence of prolonged exposure to light, elevated temperatures andhigh humidities. Other objects will be apparent from the followingdescription of the invention.

According to our invention these and other objects are accomplished bycontacting the dye image containing a completely processed colorphotograph that is substantially free from developed silver, silverhalide and soluble salts, with an aqueous solution containing astabilizing compound having at least one tri(hydroxymethyl)methyl group.The photographic element is allowed to remain in contact with the saidsolution until said element is impregnated with the said stabilizingcompound, and then the said element is dried while it still contains asubstantial quantity of the said compound.

3 Our polymethylol stabilizing compounds are advantageously representedby the formula:

in which n is an integer of from 1 to 2; and W represents a memberselected from the class consisting of carboxy and an amino group.

Our stabilizing compounds include those represented by the formula:

wherein a and [7, each represents an integer of from to l; f, g and 1'each represents an integer of from 1 to 2; R R and R each representshydrogen or hydroxyl; R and R each represents hydrogen or hydroxymethyl;R and R each represents hydrogen or together represent an oxygen atom;and the salts formed by adding HX wherein X represents an acid anion(e.g., chloride, bromide, iodide, perchlorate, sulfate, acetate,propionate, citrate, etc.) to one or both nitrogen atoms in the aboveformula.

Typical stabilizing compounds used to illustrate our invention includethe following:

(1) 3-hydroxy-2,2-dihydroxymethyl-propionic acid (2)2-amino-2-hydroxymethylpropane-1,3-diol (3)2,2,8,8-tetrahydroxymethyl-3,7-diazanonanel ,5,

9-triol dihydrochloride (4)3,2-hydroxyethyl-8,8-dihydroxymethyl-3,7-diazanonane-l,5,9-trioldihydrochloride (5) 2,2-dihydroxymethyl-3-azapentane-l,S-diolhydrochloride Compound 2 is sometimes known as tris-buffer. Compounds 3to 5 are derivatives of compound 2 and can be prepared by the method ofPierce and Wotis, J. American Chemical Soc., 66, 880 (1944). Many of ourcompounds are available. Those that arent are readily prepared by themethods described in the said reference, US. Patent 2,408,096, etc.

Although our stabilizing compounds are used to advantage in aqueoussolutions over a wide range of concentrations, it is preferred that theconcentration be at least 2.5% by weight, and a concentration ofapproximately 10% by weight often being particularly suitable. It isalso preferred that the solution be neutral or acidic, because in somecases the use of an alkaline solution may result in the formation ofyellow print-out when the treated photograph is exposed to large amountsof light. When it is necessary to neutralize or acidify the solution, amineral acid, such as hydrochloric acid, or an organic acid such ascitric acid can be used.

The aqueous solution of our invention may contain additional solutesincluding, for example, bulfering agents, preservatives for inhibitingmold growth in the solution, and known stabilizing agents. Only soluteswhich are shown not to seriously interfere with the stabilizationproduced by our stabilizing compounds should be included in thesolution.

The process of the invention can be carried out either during theprocessing procedure used for the production of a color photograph,before the latter has been dried, or afterwards.

In some cases it may be possible to modify a processing procedure so asto comprise a process of the invention simply by including apolymethylol compound in the solution last used in the procedure.

In carrying out the process of the invention, it is often convenient toimmerse the photograph completely in the stabilizing solution, but it issometimes preferable to apply the solution only to the image side whichcan be done by spraying, for example. The solution should be left incontact with the image side of the photograph for a few minutes (a timeof from 5 to 10 minutes is generally adequate) to allow theimage-containing water-permeable layers to be impregnated with thepolymethylol compound. It is generally satisfactory and convenient tocarry out the treatment at room temperature.

It is usually desirable to remove surplus stabilizing solution from atreated color photograph before drying. This can be done by squeegeeing.If more thorough removal of surplus solution is needed, as can be thecase when the color photograph has a non-absorbent support such as filmbase, the photograph can be momentarily rinsed, but care must be takento leave enough of the polymethylol compound in the photograph tostabilize the image.

Our invention is still further illustrated by means or the followingtypical examples.

Example 1 Two identical sets of color processed multilayer multicolorreversal film with cyan, magenta and yellow dye images were prepared.The films were substantially free of silver, silver halide and solublesalts. One set was treated for 10 minutes in an aqueous solutioncontaining 9% of stabilizing compound No. 1 buffered to a pH of 7 withsodium hydroxide solution. The treated transparencies were squeegeed andallowed to dry. The other set was treated with water for 10 minutes andthen dried. One-half of each set of transparencies was held as a controlwhile the other half of each set was exposed for two weeks to light froma SOO-Watt tungsten lamp at a distance of 8 /2 inches. Thetransparencies were stored at about 25 C. A comparison of the exposedtransparencies with the controls showed that there was a considerableimprovement in magenta and yellow dye stabilities in the transparenciestreated with the stabilizing compound t solution.

Example 2 Example 1 was repeated using a 10% aqueous solution ofstabilizing compound No. 2 that was adjusted to a pH of 7.0 withhydrochloric acid. The magenta and yellow image dye stabilities toprolonged exposures to the tungsten lamp were substantially improved asa result of the stabilizing treatment.

Example 3 Example 2 was repeated using a 10% aqueous solution ofstabilizing compound No. 3. Substantial improvements were made in thestability of the magenta and yellow image dyes to prolonged exposure totungsten illumination.

Example 4 Example 2 was repeated using a 10% solution of stabilizingcompound No. 4. Substantial improvements were made in the stability ofthe magenta and yellow image dyes to prolonged exposure to tungstenillumination.

Example 5 Example 2 was repeated using a 10% solution of stabilizingcompound No. 5. As in the preceding examples, the light stability of themagenta and yellow image dyes were substantially increased by thestabilizing treatment.

Example 6 Examples 1 and 2 were repeated using another multilayer,multicolor commercial reversal film product and a reversal color printmaterial. In each case substantial improvement was produced in thestability of the magenta and yellow dye images to prolonged exposure totungsten light.

Example 7 Three different multilayer multicolor print materials A, B andC containing different magenta and different yellow dye-forming couplerswere exposed to a color image and given complete color processing.One-half of the processed samples were treated for 10 minutes at 70SOUTH WINDOW FADING color photographs caused by prolonged exposure tolight may be shown when still other stabilizing solutions of ourinvention are used to treat the completely processed color photographprior to the light exposure.

The invention has been described in detail with particular reference topreferred embodiments thereof but it will be understood that variationsand modifications can be eitected within the spirit and scope of theinvention as defined hereinabove and as described in the appendedclaims.

We claim:

1. The method of inhibiting the discoloration of com- Percentage DyeDensity Loss From an Initial Density of 1.0 Stabilizing Bath TreatmentCyan Magenta Yellow Color Print Material:

A None 10 86 29 A Compound No. 2.-.- 14 32 22 B- one 9 41 94 B CompoundNo. 2.-.- 5 32 70 C None 16 98 38 C Compound No. 19 53 38 NORTH WINDOWFADING Percentage Dye Density Loss From an Initial Density of 1.0Stabilizing Bath Treatment Cyan Magenta Yellow Color Print Material"None 10 40 19 r Compound No. 2...- 14 18 17 one 8 23 73 Compound No.2..-. 11 19 41 C None 96 26 C Compound No. 2.... 15 39 32 FADE OMETE RPercentage Dye Density Loss From an Initial Density of 1.0 Stain ChangeColor Print Stabilizing Bath Magen- Magen- Material Treatment Cyan taYellow Cyan ta Yellow 12 23 18 01 02 01 14 18 10 .01 .01 .01 one 6 14 5501 02 05 Compound No. 2. 11 19 18 01 01 01 None 13 44 28 01 0 14 CCompound No. 2.-.. 34 21 01 01 01 The data show that the percent loss inmagenta dye in color prints from prolonged exposure to north windowlight was reduced from as high as 96% to 39% and that the percent lossin magenta dye in color prints from prolonged exposure to south windowlight was reduced from as high as 86% to 32% by treatment with anaqueous solution of stabilizing compound No. 2.

The data show that the percent loss in yellow dye in color prints fromprolonged exposure to light from a north window was reduced from as highas 73% to 41% and from prolonged exposure to a xenon arc Fadeometer wasreduced from as high as 55% to 18% by treatment with an aqueous solutionof stabilizing compound No. 2.

The cyan dye density loss was generally small compared to the loss inmagenta and yellow in untreated color prints.

Improvements in yellow stain in color prints given prolonged exposure inthe Fadeometer were as high as from an increase in yellow stain of H 14to a reduction of .01 as a result of treatment with our solution ofstabilizing compound No. 2.

Similar reductions in the discoloration of processed of a compoundhaving the formula:

R1 R2 R3 CH2OH R5 (H0CHZ)3C[NH(CHCH)B(CHMr-I R4-C-R5 Jo]i-1H EX g-lwherein a and b each represent an integer of from 0 to l; f, g and ieach represent an integer of from 1 to 2 such that at least one of f, gand i represents the integer 2; R R and R each represents a memberselected from the class consisting of hydrogen and hydroxyl; R and Reach represent a member selected from the class consisting of hydrogenand hydroxymethyl; R and R each represent a member selected from theclass consisting of hydrogen and when taken together an oxygen atom; andX represents an acid anion and (2) allowing said photograph to drycontaining sufficient absorbed compound to inhibit said discolora tionof said photograph.

2. The method of inhibiting the discoloration of completely processedcolor photographs caused by prolonged exposure 'to light, elevatedtemperatures and elevated humidities, said photographs beingsubstantially free of silver, silver halide and soluble salts, saidmethod comprising the steps of:

(1) imbibing in said photograph an aqueous solution of a compoundselected from the class consisting of:

3-hydroxy-2,2-dihydroxymethylpropionic acid,

2-amino-2-hydroxymethylpropane-1,3-diol,

2,2,8,8-tetrahydromethyl 3,7 diazanonane 1,5,9-

triol dihydrochloride,

3,2 hydroxyethyl 8,8 dihydroxymethyl 3,7-

diazanonane-1,5,9-triol dihydrochloride, and

2,2 dihydroxymethyl 2- azapentane 1,5 diol hydrochloride,

(2) allowing said photograph to dry containing sufficient absorbedcompound to inhibit said discoloration of said photograph.

3. The method of inhibiting the discoloration of completely processedcolor photographs caused by prolonged exposure to light, elevatedtemperatures and elevated humidities, said photographs beingsubstantially free of silver, silver halide and soluble salts, saidmethod comprising the steps of:

(1) imbibing in said photograph an aqueous solution of a compound 3hydroxy 2,2 dihydroxymethylpropionic acid,

(2) allowing said photograph to dry containing sufficient absorbedcompound to inhibit said discoloration of said photograph.

4. The method of inhibiting the discoloration of completely processedcolor photographs caused by prolonged exposure to light, elevatedtemperatures and elevated humidities, said photographs beingsubstantially free of silver, silver halide and soluble salts, saidmethod comprising the steps of:

(l) imbibing in said photograph an aqueous solution of a compound2-arnino-2-hydroxymethylpropane- 1,3-diol,

(2) allowing said photograph to dry containing sufficient absorbedcompound to inhibit said discoloration of said photograph.

5. The method of inhibiting the discoloration of completely processedcolor photographs caused by prolonged exposure to light, elevatedtemperatures and elevated humidities, said photographs beingsubstantially free or silver, silver halide and soluble salts, saidmethod comprising the steps of:

(1) imbibing in said photograph an aqueous solution or a compound2,2,8,8 tetrahydromethyl 3,7 diazanonane-l,5,9-triol dihydrochloride,

(2) allowing said photograph to dry containing sufficient absorbedcompound to inhibit said discoloration of said photograph.

6. The method of inhibiting the discoloration of completely processedcolor photographs caused by prolonged exposure to light, elevatedtemperatures and elevated humidities, said photographs beingsubstantially free or silver, silver halide and soluble salts, saidmethod comprising the steps of (l) imbibing in said photograph anaqueous solution of a compound 3,2-hydroxyethyl 8,8dihydroxymethyl-3,7-diazanonane-1,5,9-triol dihydrochloride.

(2) allowing said photograph to dry containing sufficient absorbedcompound to inhibit said discoloration of said photograph.

7. The method of inhibiting the discoloration of completely processedcolor photographs caused by prolonged exposure to light, elevatedtemperatures and elevated humidities, said photographs beingsubstantially free of silver, silver halide and soluble salts, saidmethod com prising the steps of:

(1) imbibing in said photograph an aqueous solution of a compound2,2-dihydroxymethyl 3 azapentane- 1,5-diol hydrochloride,

(2) allowing said photograph to dry containing sut" ficient absorbedcompound to inhibit said discoloration of said photograph.

References Cited UNITED STATES PATENTS 2,384,663 9/1945 Weissberger etal 96 56 2,487,569 11/1949 Mackey 96-56 3,095,302 6/1963 Jeifreys et al96-56 3,157,504 11/1964 Bard 9656 I. TRAVIS BROWN, Primary Examiner"H950 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,L}.73, 9 9 Dated '1 0/21 /69 Inventor) Jeffrey's and Williams It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

601. 7, line H between dihydroxymethyl" and "-azapentene", I

delete "2" and substitute in its place -3--.

SIGNED MD CELEB JANE 1S7] EEAL Attest:

M. Fletcher, Ir. m E. JR. Attesnng Officer Patents

